n : either of two nerves that arise mostly from the second cervical nerve: a : the medial branch of the second cervical nerve that innervates the scalp at the top of the head - called also greater occipital nerve b : one arising from the second cervical nerve or from the loop between the second and third cervical nerves and innervating the scalp esp. in the lateral area of the head behind the ear - called also lesser occipital nerve .